The invention relates to an integrated turboramjet engine for a hypersonic airplane having a common air inlet for the turbo-circuit and the ramjet circuit. An annular turbo-inlet duct and a ram air inlet duct which concentrically surrounds this turbo-inlet duct are provided. On the exterior side the ram air inlet is delimited by an engine casing. An inlet cone and movable devices for the deflecting of the air current from the common air inlet into one of the two inlet ducts is provided.
Endeavors are taking place to develop hypersonic airplanes which can take off and land on normal airports and develop cruising speeds of several Mach. Hypersonic airplanes of this type may be used either as fast long-distance transport planes or as normally starting space tugs. The achievable Mach numbers range between Mach 4 and 8 at flying altitudes of approximately 30 km.
Engines for propelling such airplanes must meet a number of requirements which cannot be reached by means of conventional engine concepts. Thus, a sufficient power output must take place at low flying speeds below Mach 1 up to the peak speeds. For this purpose, it was suggested to provide combined turboramjet engines which at low flying speeds operate as a gas turbo-engine with or without an afterburner and, above a certain flying speed, operate as ramjet engines (RAM-operation).
A construction of such engines provides that a gas turbo-engine is equipped on both sides with flaps, and an afterburner downstream of the gas turbine is simultaneously used as a ramjet burner chamber. For this purpose, an annular ram air duct is provided concentrically outside the gas turbine through which, during ramjet operation, the inflowing air is guided directly into the combustion chamber while bypassing the gas turbine. For this purpose, movable guide plates are provided in the area of the inlet duct and behind the turbine, these guide plates selectively guiding the air current either into the concentrically interior turbo-inlet duct and thus through the gas turbine core engine, or into the concentrically exterior ram air inlet duct.
It is a considerable problem in the case of such change-over engines that the outside diameter of the engine must be kept as small as possible. Its minimum measurement is determined by the cross-sections of the two inlet ducts as well as the inside diameter required in the hub area for the core engine.
A conceivable, constructively very simple possibility for the alternative acting upon the inlet ducts consists of providing an axially slidable guide plate ring which, in a first position, closes off the ram air inlet duct and in a second position closes off the turbo-inlet duct. However, this type of a solution has the disadvantage that the inlet duct carry out up complex courses and an outside diameter of the engine is required which exceeds the minimum diameter. Such enlargements of the diameter which are in the range of several decimeters, at high speeds, because of the enlarged cross-sectional surface, result in an increased flow resistance.
It is therefore an object of the present invention to develop a turboramjet engine of the above-mentioned type such that a deflection of the air current into the two inlet ducts is possible without the requirement of an enlargement of the outside diameter of the engine.
According to the invention, this object is achieved by means of an arrangement, wherein the devices for the deflecting of the air current comprise a guide ring which can be displaced in the axial direction along the engine casing for the closing-off of the ram air duct as well as an annular cone which is disposed radially inside with respect to the guide ring and can be displaced in the opposite direction for the closing-off of the turbo-inlet duct, the contour of the guide ring forming the duct wall and the annular cone having a construction which is advantageous with respect to the flow.
The principal advantage of the invention is that despite the fact that the minimum diameter defined by the inlet ducts is maintained, a deflection of the air current into the two inlet ducts is possible, in which case, at the same time, a low-loss housing contour of the flow ducts can be achieved. In addition, by means of this arrangement, a maintaining of the engine output is also achieved in the critical moment of the change-over from the turbo-operation to the ramjet operation in that the approaching air, in a targeted and continuous manner, can be deflected from one inlet duct in connection with the closing device behind the turbine into the other inlet duct. Additional advantages of the invention are the short installation length of the closing device and the short strokes of the adjusting arrangements. Also, during the ramjet operation, good cooling possibilities exist for the thermally stressed inlet cone and the annular cone by means o film cooling as a result of the blowing-in of cold air.
In an advantageous further development of the invention, the guide ring has an approximately conically tapering front side and a connecting approximately conically tapering rear side. The guide ring is therefore constructed to be approximately wedge-shaped, in which case the front side is shaped out for forming an aerodynamically advantageous flow contour of the turbo-inlet duct during the turbo-operation In this operating condition, the guide ring is in its axial rear position, and its front side is advantageously shaped such that the wall contour from the outside casing to the intermediate casing, which at the same time also represents the outer boundary of the turbo-inlet duct, causes the lowest possible flow losses. The rear side of the guide ring is developed such that, while interacting with the annular cone, during the ramjet operation, it defines an annular duct connected with a ram air inlet duct. For this purpose, the rear side is preferably constructed to be conical.
During the ramjet operation, the guide ring is in its axially frontal position, in which case, at the same time, the annular cone is arranged slightly behind and radially inside the guide ring. In this case, the rear side of the guide ring defines the frontal section of the exterior wall of the ram air inlet duct. At the same time, the annular cone is shaped such that a continuous flow course is possible from the inlet cone to the intermediate casing.
The ring edge between the front side and the rear side of the guide ring is also shaped such that during the ramjet operation a flow loss occurs in this area that is as low as possible.
Another advantageous development of the invention consists of the fact that the frontal axial position of the annular cone is fixed in such a manner that the annual duct formed between the annular cone and the inlet cone has at least the cross-section of the ram air inlet duct. This arrangement has the advantage that during the changing-over from the turbo-operation to the ramjet operation, after the opening of the ram air inlet duct, sufficient air can be admitted to the ram air inlet duct by the advancing of the guide ring.
A further development according to the invention provides that, for the changing-over from the turbo-operation to the ramjet operation, the guide ring can first be slid from an axially rear position toward the front, and subsequently, the annular cone is displaced from an axially frontal position toward the rear. Approximately at the same time with the advancing of the guide ring, a closing flap will close arranged downstream of the core engine so that no more air is taken into the turbo-inlet duct; i.e with the advancing of the guide ring, the ram air inlet duct is opened up and the approaching air is guided into it. Then the annular cone is moved from a frontal position toward the rear and, in its end position, closes off the turbo-inlet duct completely.
As an alternative, it is also possible to carry out the two movements of the guide ring and the annular cone in opposing directions not successively but partly or completely simultaneously. As a result, the change-over time from the turbo-operation to the ramjet operation and vice versa can be advantageously shortened.
The annular cone preferably has the continuation of the contour of the inlet cone and, if required, may have a bend, preferably a convex bend viewed from the inflow direction, if the inlet cone has a bend of this shape.
The annular cone can be moved axially by means of adjusting devices, in which case, at the same time, the axial guiding and locking in certain positions will take place.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.